The water treatment device removes impurities in water by adsorbing and removing cations or anions by ion exchange resin. In the water treatment device, a bipolar membrane may be used in which a cation exchange group is disposed in one surface, and an anion exchange group is disposed in another surface (e.g., refer to PTL 1).
As the above-described bipolar membrane of the water treatment device, a textured membrane in which peaks and bottoms are arranged at intervals has been known (e.g., refer to PTL 1).
FIG. 13 is a schematic view showing a schematic configuration of the textured membrane disclosed in PTL 1.
As shown in FIG. 13, textured membrane 205 disclosed in PTL 1 has cation exchange layer 201 and anion exchange layer 202 adjacent to cation exchange layer 201, and peaks 203 and bottoms 204 are arranged at intervals. Since a surface area of the membrane is increased by peaks 203 and bottoms 204 formed in this textured membrane 205, when water containing a hardness component is supplied to textured membrane 205, an adsorption speed of the hardness component can be increased. Moreover, in peaks 203 and bottoms 204 of textured membrane 205, if a plurality of textured membranes 205 are used, a passage of treated water is formed as indicated by arrow 206 between each of peaks 203 and each of bottoms 204, so that a pressure loss can be kept low.
Moreover, in PTL 1, there has been disclosed an electrochemical cell in which electrode 207 and electrode 208 are disposed on both sides of textured membrane 205. In the electrochemical cell disclosed in PTL 1, a voltage is applied to both the electrodes in the presence of water, and the water is disassociated at interface 209 between cation exchange layer 201 and anion exchange layer 202 to generate H+ and OH−. These H+ and OH− are substituted with cations and anions adsorbed by cation exchange layer 201 and anion exchange layer 202, which allows cation exchange layer 201 and anion exchange layer 202 to be reproduced. Therefore, in the electrochemical cell disclosed in PTL 1, the reproduction need not be performed, using a chemical agent as in the related art.
Moreover, there has been known a device including a variable voltage supply source capable of maintaining electrodes at a plurality of voltage levels during an ion exchange stage (e.g., refer to PTL 2). In the device disclosed in PTL 2, by maintaining the electrodes at the plurality of voltage levels, an ion concentration of a flowing-out solution flowing out from the device can be controlled.
However, even the water treatment device using textured membrane 205 disclosed in PTL 1 has had room for improvement in view of uniformization of flow of the water inside the device. Moreover, in the device disclosed in PTL 2, when the bipolar membrane is reproduced, there has been room for improvement in view of suppression of formation of scale.